We have discovered a novel gene that may play a role in HIV-1 disease progression. This is suggested by its deletion or mutation in many long-term survivors (LTS), who are HIV-1 infected individuals who have not progressed to symptoms of AIDS for many years and who have evidence of an attenuated virus. We propose in this grant to further characterize the protein (HAP) encoded in this gene, to develop a DNA vector capable of efficiently expressing the protein (HAP-DNA), and targeting HAP-DNA delivery to dendritic cells (DCs). We will also examine simian immunodeficiency virus (SIV) sequences for evidence of an analogous gene, inasmuch as SIV infection of rhesus macaques represents a model for AIDS pathogenesis. We further want to determine HAP's immunogenicity. To determine this, we plan to study peripheral blood lymphocytes (PBL) or purified T cells, obtained from HIV-1 infected or non-infected individuals, following stimulation in vitro with autologous DCs pulsed with HAP-DNA or control-DNA(s). Quantification of proliferation, as well as the activation state and cytokine profile (IFN-g, IL-4, TNF-a), of T cell subsets, will be determined following HAP peptide presentation by HAP-DNA pulsed, autologous dendritic cells (DCs) using both flow cytometry, and an enzyme-linked immunospot (ELISPOT) assay for IFN-g release. Studies to determine the state of DC differentiation that will facilitate induction of cellular immunity and TH1 polarization, will be explored as a mechanism of expanding ex vivo primary immune responses to the HAP protein. These studies will help determine the potential and viability of HAP-DNA as a future HIV-1 DNA vaccine candidate.